Pressure-induced superconductivity and structural transitions in Ba(Fe_(0.9)Ru_(0.1))_2As_2

摘要

Electrical transport and structural characterizations of isoelectronically substituted Ba(Fe_(0.9)Ru_(0.1))_2As_2 have been performed as a function of pressure up to ～30 GPa and temperature down to ～10 K using designer diamond anvil cell. Similar to undoped members of the AFe_2As_2 (A = Ca, Sr, Ba) family, Ba(Fe_(0.9)Ru_(0.1))_2As_2 shows anomalous a-lattice parameter expansion with increasing pressure and a concurrent ThCr_2Si_2 type isostructural (I4/mmm) phase transition from tetragonal (T) phase to a collapsed tetragonal (cT) phase occurring between 12 and 17 GPa where the a is maximum. Above 17 GPa, the material remains in the cT phase up to 30 GPa at 200 K. The resistance measurements show evidence of pressure-induced zero resistance that may be indicative of high-temperature superconductivity for pressures above 3.9 GPa. The onset of the resistive transition temperature decreases gradually with increasing pressure before completely disappearing for pressures above ～10.6 GPa near the T-cT transition. We have determined the crystal structure of the high-Tc phase of Ru-doped BaFe_2As_2 to remain as tetragonal (I4/mmm) by analyzing the X-ray diffraction pattern obtained at 10 K and 9.7 ± 0.7 GPa, as opposed to inferring the structural transition from electrical resistance measurement, as in a previous report [S.K. Kim, M.S. Torikachvili, E. Colombier, A. Thaler, S.L. Bud'ko, P.C. Canfield, Phys. Rev. B 84, 134525 (2011)].